The present invention relates generally to an implement supported on caster wheels, and more specifically to a device for controlling caster wheel motion.
Caster wheels are commonly used on agricultural equipment to prevent skidding of a wheel or wheels when the implement is turned. These wheels can cause a problem when transporting the machine at higher than field-operating speeds by wobbling or attempting to rotate about their caster frame vertical spindle. This action can cause such problems as tire wear, structural damage or loss of control of the machine. In some previously available implements with caster wheels, the caster wheels have been rigidly pinned to prevent oscillation, but such an arrangement causes the wheel to skid and results in high stresses in the structural members when the implement is turned.
Other previously available devices, such as the caster wheel assembly shown in U.S. Pat. No. 2,761,692 include a friction disk fixed to the spindle and engaging a friction plate interlocked with the framework and spring-urged downwardly. Such a device is relatively expensive, since it requires special castings or the like. Swivel wheel dampers for the caster wheels of aircraft 20 have also been available for some time, but these devices are also relatively complicated and expensive to manufacture. Examples of such aircraft devices are shown in U.S. Pat. Nos. 2,367,993; 2,482,961; 2,508,057; 2,693,003 and 2,770,832. U.S. Pat. No. 2,388,874 shows a caster wheel with an arm that is spring-loaded to restore the wheel to its operating position from any castered position. At transport speeds, wobbling would still be present with such a device.
In certain applications, such as when a seeder is towed behind a grain cart, and the grain cart, in turn, is towed behind a tractor or the like, the cart is supported on four caster wheels spaced fore-and-aft in pairs. In some situations it is desirable that all the wheels be able to caster freely, while in other situations it is necessary to limit the castering of a front or rear pair of wheels while permitting the remaining wheels to caster freely. Heretofore, devices for selectively locking the caster wheel in position or alternately adjustably braking the caster action have been relatively expensive or ineffective and often have been difficult to adjust for the proper caster wheel action.